Oliva Ricardo F, Cano Liliana M, Raffaele Sylvain, Win Joe, Bozkurt Tolga O, Belhaj Khaoula, Oh Sang-Keun, Thines Marco, Kamoun Sophien
1 The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, United Kingdom;
2 Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-742, Korea;
Mol Plant Microbe Interact. 2015 Aug;28(8):901-12. doi: 10.1094/MPMI-12-14-0393-R. Epub 2015 Jul 17.
The introgression of disease resistance (R) genes encoding immunoreceptors with broad-spectrum recognition into cultivated potato appears to be the most promising approach to achieve sustainable management of late blight caused by the oomycete pathogen Phytophthora infestans. Rpi-blb2 from Solanum bulbocastanum shows great potential for use in agriculture based on preliminary potato disease trials. Rpi-blb2 confers immunity by recognizing the P. infestans avirulence effector protein AVRblb2 after it is translocated inside the plant cell. This effector belongs to the RXLR class of effectors and is under strong positive selection. Structure-function analyses revealed a key polymorphic amino acid (position 69) in AVRblb2 effector that is critical for activation of Rpi-blb2. In this study, we reconstructed the evolutionary history of the Avrblb2 gene family and further characterized its genetic structure in worldwide populations. Our data indicate that Avrblb2 evolved as a single-copy gene in a putative ancestral species of P. infestans and has recently expanded in the Phytophthora spp. that infect solanaceous hosts. As a consequence, at least four variants of AVRblb2 arose in P. infestans. One of these variants, with a Phe residue at position 69, evades recognition by the cognate resistance gene. Surprisingly, all Avrblb2 variants are maintained in pathogen populations. This suggests a potential benefit for the pathogen in preserving duplicated versions of AVRblb2, possibly because the variants may have different contributions to pathogen fitness in a diversified solanaceous host environment.
将编码具有广谱识别能力的免疫受体的抗病（R）基因渗入栽培马铃薯中，似乎是实现对卵菌病原体致病疫霉引起的晚疫病进行可持续管理的最有前景的方法。基于初步的马铃薯病害试验，来自茄科酸浆的Rpi-blb2在农业应用中显示出巨大潜力。Rpi-blb2在致病疫霉无毒效应蛋白AVRblb2转运到植物细胞内后，通过识别该蛋白赋予免疫性。这种效应蛋白属于RXLR类效应蛋白，且处于强烈的正选择之下。结构功能分析揭示了AVRblb2效应蛋白中一个关键的多态性氨基酸（第69位），它对于激活Rpi-blb2至关重要。在本研究中，我们重建了Avrblb2基因家族的进化历史，并进一步表征了其在全球种群中的遗传结构。我们的数据表明，Avrblb2在致病疫霉的一个假定祖先物种中作为单拷贝基因进化而来，最近在感染茄科寄主的疫霉属物种中有所扩展。因此，致病疫霉中至少出现了四种AVRblb2变体。其中一种变体在第69位有一个苯丙氨酸残基，可逃避同源抗性基因的识别。令人惊讶的是，所有Avrblb2变体都在病原体种群中得以保留。这表明保留AVRblb2的重复版本对病原体可能有潜在益处，可能是因为这些变体在多样化的茄科寄主环境中对病原体适应性可能有不同贡献。
